Crack Width of Partially Prestressed Concrete

[Edvinas]

Hi guys, i am doing a thesis on partially prestressed concrete beams and can't seem to predict the crack widths of my beam. Could anyone point me to the right direction and tell me where i could find a formula for the crack width of partially prestressed concrete? The examples that i did ended up giving me a crack width with a minus sign, which i think must be the wrong answer?

 

[rapt]

Some information might be helpful, like which design code.

Eurocode has a reasonable method.

 

[cooperDBM]

Before doing a cracked analysis you should do an uncracked analysis to make sure there is enough load to crack the beam.

As a start some older classic papers on the subject are,

"Steel Stresses in Partially Prestressed Concrete Members", K.M. Suri, W.H. Dilger, PCI Journal, Vol. 31, No. 3, May-Jun 1986, pp 88-112

"Crack Width of Partially Prestressed Concrete Members", K.M. Suri, W.H. Dilger, ACI Journal, Vol. 83, No. 5, Sep-Oct 1986, pp 784-797

"Analysis of Cracked Prestressed Concrete Sections: A Practical Approach", R. Mast, PCI Journal, Vol. 43, No. 4, Jul-Aug 1998, pp 80-91

There are many others. PCI papers can be found for free on the PCI web site.

 

[rapt]

Prestressed concrete in most of the world is considered to have no tensile strength, the same as reinforced concrete.

So if it is in tension, it is cracked.

Many codes provide a tension limit that allows a deemed to comply check on cracking, so if the tension is below this limit, the crack widths are assumed to be ok without further calculation, but the concrete is still assumed to be cracked if it is in tension.